Muon capture is the capture of a negative muon by a proton, usually resulting in production of a neutron and a muon neutrino, and sometimes a gamma photon.
Except for the flavor of neutrino, it has exactly the same result as electron capture, except that the great mass-energy of the muon makes it allowed for all nuclei and there is so much excess energy that a nucleus can disintegrate; for heavy nuclei this leads to emission of nuclear particles; most often neutrons, but charged particles can be emitted as well.
Ordinary muon capture (OMC) involves capture of a negative muon from the atomic orbital without emission of a gamma photon:
+ → μ +
Radiative muon capture (RMC) is a radiative version of OMC, where a gamma photon is emitted: + → μ + +
Theoretical motivation for the study of muon capture on the proton is its connection to the proton's induced pseudoscalar form factor gp '
The most precise measurement of the muon capture rate on the proton 𝛬𝑆 =(714.9 ±5.4stat ±5.1syst) s−1 and the induced pseudoscalar coupling constant gp=8.06 ±0.55 was done by the MUCAP experiment [2,3] with a measurement performed at the Paul Scherrer Institut, Switzerland. The result is in excellent agreement with theoretical predictions .
Nuclear waste disposal Muon capture is being investigated for practical application in radioactive waste disposal, for example in the artificial transmutation of large quantities of long-lived radioactive waste that have been produced globally by fission reactors. Radioactive waste can be transmuted to stable isotopes following irradiation by an incident muon () beam from a compact proton accelerator source.
References
V.A.Andreev et al, (2013) "Measurement of Muon Capture on the Proton to 1% Precision and Determination of the Pseudoscalar Coupling 𝑔𝑃" Physical Review Letters 110 (3) 012504 DOI: https://doi.org/10.1103/PhysRevLett.110.012504
Nagamine, Kanetada (2016) "Nuclear Waste Disposal Method and its apparatus using muon-nuclear-absorption". (WO2016143144A1) Espacenet (Patent database).